erc-c/include/vm_screen.h

#ifndef _VM_SCREEN_H_
#define _VM_SCREEN_H_

#include <stdbool.h>
#include <SDL.h>

typedef struct {
    /*
     * These are the x and y coordinate offsets in the logical dimension
     * established in a vm_screen. An offset of (0, 0) would be in the
     * top-left; (5, 5) would be 5 pixels down, and 5 pixels to the
     * right, of that top-left corner.
     */
    int xoff;
    int yoff;

    /*
     * These are the width and height of the area we're defining. A
     * single pixel in the logical area would have a width and height of
     * (1, 1); use larger numbers to indicate a larger square (if the
     * two are equal) or rectangle (if unequal).
     */
    int width;
    int height;
} vm_area;

typedef struct {
    /*
     * This is the window in SDL that we're displaying. It's fine for a
     * screen to be headless; that is, not to have a window. Screen
     * functions which deal with SDL will simply not run that code if
     * headless.
     */
    SDL_Window *window;

    /*
     * In SDL, the renderer is comparable to the old SDL_Surface type
     * (which is still there!). A renderer is a little more stateful; it
     * contains its own color information to be used when rendering
     * shapes, for example.
     */
    SDL_Renderer *render;

    /*
     * These are the x and y coordinates of the window we're creating.
     * FIXME: this should probably be renamed to width and height...
     */
    int xcoords;
    int ycoords;
} vm_screen;

/*
 * Set the contents of an SDL_Rect to the equivalent fields contained in
 * a vm_area.
 */
#define SET_SDL_RECT(name, a) \
    (name).x = (a).xoff; \
    (name).y = (a).yoff; \
    (name).w = (a).width; \
    (name).h = (a).height

/*
 * Much like SET_SDL_RECT(), except this will (as a side-effect!)
 * declare an SDL_Rect variable (`name`) and pass that into the SET
 * macro.
 */
#define MAKE_SDL_RECT(name, a) \
    SDL_Rect name; \
    SET_SDL_RECT(name, a)

extern bool vm_screen_active(vm_screen *);
extern void vm_area_set(vm_area *, int, int, int, int);
extern int vm_screen_add_window(vm_screen *, int, int);
extern int vm_screen_init();
extern int vm_screen_xcoords(vm_screen *);
extern int vm_screen_ycoords(vm_screen *);
extern vm_screen *vm_screen_create();
extern void vm_screen_draw_rect(vm_screen *, vm_area *);
extern void vm_screen_finish();
extern void vm_screen_free(vm_screen *);
extern void vm_screen_refresh(vm_screen *);
extern void vm_screen_set_color(vm_screen *, uint8_t, uint8_t, uint8_t, uint8_t);
extern void vm_screen_set_logical_coords(vm_screen *, int, int);

#endif